The present inventors proposed a geothermal heat exchanger which comprises a liquid lowering pipe to lower a heat exchange liquid pressurized and supplied by a high-pressure liquid supply pump and a liquid raising pipe to raise the heat exchange liquid in a state without vapor heated by heat from a geothermal zone, feeds the heat exchange liquid extracted from the liquid raising pipe into a steam generator and extracts only steam therefrom. This geothermal heat exchanger is structured in such a manner that the liquid lowering pipe is disposed on the side of an outer circumference of the liquid raising pipe, and the heat exchange liquid is transported through introducing holes provided at a lower part of the liquid lowering pipe to the liquid raising pipe.
Such a geothermal heat exchanger is an effective invention because impurities do not adhere to the apparatus for the use of steam and a thermal-efficient heat exchange can be realized with very little influence on the environment in the vicinity of the geothermal zone since steam can be obtained from a hot liquid in a high temperature and a high pressure, extracted from the underground.